The Platypus—God’s Little Joke—Can Be Killed by River Dams

Australian platypus populations are becoming increasingly isolated as their habitats are fragmented by human-made barriers. As a result, the long-term survival of this unique species is threatened.

A 2020 report estimated that the area occupied by the beloved platypus has shrunk by at least 22 percent over the past 30 years. The species has recently been classified as “Near Threatened” by the International Union for Conservation of Nature due to declining populations.

Swimming platform
A file photo of a swimming platypus. The unique species is classified as Near Threatened by the IUCN.

Large dams, more than 30 feet high, pose a significant threat to freshwater species such as platypuses by restricting their migration and changing seasonal flow patterns. In a study, published by the journal Nature Communications BiologyLuis Mijangos and colleagues used DNA analysis to study the impact of dam construction on platypus populations.

“In our study, we use genetic variation to give us an idea of ​​whether platypuses are able to get around dams,” Mijangos said. Newsweek. “We found that genetic differentiation between groups above and below dams was much higher than genetic differentiation between populations in rivers without dams, and that this genetic differentiation increased linearly over time.

“These results suggest that little or no platypuses have passed around the dams since they were built, so we can now be more confident that the dams are probably impassable barriers for platypuses.”

This fragmentation poses a serious threat to the long-term survival of the species. “When there is no connectivity between populations … the ability to repopulate available habitats or migrate to areas with more suitable conditions is limited,” Mijangos said. “Fragmentation also simultaneously reduces both local population size and gene flow, each of which would be expected to lead to increased inbreeding and a reduction in the genetic variation necessary for adaptation.”

Platypus in a towel
A flatfoot wrapped in a towel. Plaice populations are becoming increasingly fragmented due to the construction of man-made river dams.
Gilad Bino

In the face of habitat disruption, pollution, climate change and predation by invasive species, the ability to adapt to new environments becomes more important than ever. However, to be able to adapt, a species must have a diverse, well-mixed gene pool. When populations become fragmented, this genetic mixing becomes more difficult to achieve.

The platypus has previously been described as “God’s little joke” because of its unusual combination of characteristics: while it has fur and produces milk like a mammal, it also lays eggs and has a duck-like beak and feet. the male platypus produces venom from spurs on its hind legs, which, while deadly, may have potential as a treatment for diabetes. Its fur glows green under UV light and it uses its electric socket to find food underwater.

“Platypuses are arguably the most irreplaceable mammal,” Mijangos said.

The study authors recommended introducing strategies to promote mixing of the platypus population, such as developing “platypus ways” to help the animals climb over dams. Water quality and riverbank restoration will also be important and further research will be required to better understand the breeding requirements of this unique species.

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